Nitrogen Fertility Affects Bt Endotoxins

February 12, 2003 10(2):14

Joe Lauer, Corn Agronomist

In a 2003 article published by Bruns and Abel in Stoneville, MS (Agronomy Journal
95:207), it was found that nitrogen fertilizer affected the concentration of Bt
endotoxin in corn. Fertilizer was applied at rates of 0, 100, 200 and 300 lb N/A.
This resulted in Bt endotoxin levels of 350 to 534 ug/kg ( a range of 35%). It was
concluded that available N increases Bt synthesizing proteins and thus increases
Bt concentration. Adequate levels of N fertility during early growth appeared essential
for Bt production by the plant and may affect the ability of corn plants to resist
insect predation.

This result has implications for some observations in Wisconsin last year. Anecdotally
I heard of approximately 6 fields where Bt corn failed to prevent European corn
borer damage. Many reasons have been offered including seed contamination, incomplete
clean-out of the planter, cross over of large larvae from non-Bt corn hybrids, lack
of Bt expression during stress, and development of European corn borer resistance.
The above study supports the idea that periods of stress may reduce Bt concentrations
within the corn plant and may have implications for management in field situations
where stress is typically encountered. Stay tuned …